Human skin is a composite material of the epidermis and the dermis. The topmost part of the epidermis is the stratum corneum. This layer is the stiffest layer of the skin, as well as the one most affected by the surrounding environment. Below the stratum corneum is the internal portion of the epidermis. Below the epidermis, the topmost layer of the dermis is the papillary dermis, which is made of relatively loose connective tissues that define the micro-relief of the skin. The reticular dermis, disposed beneath the papillary dermis, is tight, connective tissue that is spatially organized. The reticular dermis is also associated with coarse wrinkles. At the bottom of the dermis lies the subcutaneous layer.
The principal functions of the skin include protection, excretion, secretion, absorption, thermoregulation, pigmentogenesis, accumulation, sensory perception, and regulation of immunological processes. These functions are detrimentally affected by, for example, dryness, yeast, and structural changes in the skin, such as due to aging and excessive sun exposure.
Many hair care products tend to include alkaline components, which tend to open pores in the scalp. While these products may improve or alter hair appearance, they may exacerbate various scalp conditions, such as dandruff, psoriasis, and seborrhea.
Various pharmaceuticals that frequently contain one or more alpha hydroxy acids, such as glycolic acid, have been used to prevent and treat certain cellular, skin, hair and other conditions. For example, U.S. Pat. No. 4,668,509 discloses polythioalkanecarboxylic anionic products and their preparation and use in cosmetic compositions and hair treatment compositions, such as shampoos.
U.S. Pat. No. 4,814,166 discloses polyanionic oligomer compounds suitable for use in keratin fiber treatment, such as hair, which may be administered in a shampoo. These compounds are alleged to hold hair with suppleness and without significant hardening of the hair.
U.S. Pat. No. 5,344,971 discloses mercapto acids, such as thiolactic acid (2-mercaptopropionic acid), that are used as reducing agents for the permanent reshaping of hair or for depilatory milks and creams.
An article entitled "Hydroxy Acids and Skin Aging" discloses the use of hydroxy and other acids as skin peels and emollients that can moisturize, stimulate, and exfoliate the skin. [Smith, W., Soap/Cosmetics/Chemical Specialties, pp. 54-58, 76, Sept., 1993.]. A study was conducted with hydroxy, keto, carboxylic, or dicarboxylic acids, including glycolic and salicylic acids, to determine long-term rejuvenating benefits. The study noted that higher pH formulations resulted in less stimulatory activity and lower irritation, and concluded that various non-hydroxy acids would be expected to deliver long-term rejuvenating benefits. Id. at 58.
One publication, WO 95/33438, discloses skin or hair care products having an agent acting cosmetically on the hair or skin, such as thioglycolic acid preferably with an ammonium salt. The agent is absorbed in a fibrous material containing amino groups, such as cellulose based-fiber containing polysilicic acid.
U.S. Pat. No. 5,422,370 discloses methods of using hydroxyacid or related compounds, such as alpha 2-hydroxypropanoic acid (lactic acid), for the treatment of wrinkles. These compounds are also disclosed to be effective for enhancing the topical effects of other cosmetic and pharmaceutical agents for treatment of conditions such as dry skin, ichthyosis, eczema, palmar and plantar hyperkeratoses, dandruff, acne, pruritis, psoriasis, Darier's disease, lichen simplex chronicus, and warts. Similarly, U.S. Pat. No. 5,547,988 discloses methods for reducing the appearance of skin changes associated with aging, such as wrinkles, by topically applying a compound of glycolic acid, lactic acid, citric acid, or a salt thereof.
U.S. Pat. No. 5,587,149 discloses improved stable emulsions of polyethylene glycol-in-oil for topical application to the skin that contain one or more water soluble active ingredients, such as Vitamin C, glycolic acid, and the like.
Despite these references, there is still a need for pharmaceutical compositions and methods for the prevention, treatment, and management of scalp conditions, such as dandruff, psoriasis, and seborrhea. The present invention advantageously provides pharmaceutical compositions, as well as methods for prevention and treatment, by administering such compositions to repair and normalize the scalp for the prevention and treatment of scalp conditions.